If I may verify the processing times involved in NIW. Since it falls under EB2 category, I am assuming it may be a long time before I can get my EAD card and be able to change employers. Also, I want to confirm if there could be issues if I change employers during the process - If so, I'd prefer to change my current employer before starting with it.
You can change employers any time if you are a self-applicant and will continue to work in your stated area of national interest. But NIW priority date will take the same time as a normal EB-2 application does. See: http://www.immigration.com/visa-bulletin under employment-based category 2.